Recently, portable data terminals, such as cellular phones (including a personal handy-phone system called PHS) with the Internet access capability have been widely used. Those terminals make it possible not only to make voice communications but also to provide electronic mail transmission/reception services and various services via web site access. Considering the limitation on the display screen size of a cellular phone, more and more web sites have been prepared for cellular phones.
Today, various services provided by web sites are carried out through online data transfer to and from web servers. However, because a cellular phone does not support the software capture capability that reads software from an external medium such as a CD-ROM, it is desired in the future that additional processing application programs be downloaded over the network for offline, local execution on a cellular phone.
However, as compared with non-portable data processing units such as a personal computer, the capacity of internal non-volatile storage of a cellular phone is substantially limited. In addition, at present, a cellular phone does not have a function to connect to a large-capacity external storage unit such as a hard disk drive and, even if it has such a function, the problem is that frequent connection to an external storage unit would lose the advantage of the portability of a cellular phone.
Therefore, the local execution of an additional application program (simply called an application in the specification and the drawings of the present invention) on a cellular phone has the following problems:                (1) A decrease in the free space of the internal storage unit (also called local storage) prevents new additional programs from being stored.        (2) This requires an application in the local storage to be replaced when the storage capacity becomes insufficient. However, if an application stored in the local storage is erased during application replacement and if the user paid for the application, the user must purchase the same application again the next time he or she wants to use the application. This is uneconomical for the user. If those conditions keep the user from purchasing applications, application vendors will lose the chance of sales.        (3) Such conditions as described above have prevented applications, which work on cellular phones and so on, from being sold on a network.        
In view of the foregoing, it is an object of the present invention to provide a storage area providing method and a storage server capable of storing and managing software for use on portable data terminals.
It is another object of the present invention to provide a new method for selling software for use on those portable data terminals.
It is still another object of the present invention to provide a new portable data terminal and a computer program.